A screen shot of a video taken by a San Diego TV station shows the spot where a drone struck the cruiser Chancellorsville during a targeting exercise. (Courtesy of NBC 7)

The Navy suspended all target drone operations after the cruiser Chancellorsville was struck by one during a radar exercise last month, punching a hole in the ship’s side and leaving two crew members with minor burns. Investigations are underway to determine what went wrong during this routine exercise, conducted by many ships.

Here’s what you need to know:

■What’s been suspended. Officials have stopped all flights of BQM-74E Chukar III remote-controlled target drones, the type used in the Chancellorsville’s combat systems testing, according to a spokeswoman for the Naval Air Warfare Center Weapons Division.

Officials also suspended use of the BQM-34S Firebee, another targeting drone that uses the same control system.

Substantial damage. An errant Chukar III punctured Chancellorsville’s hull during a tracking exercise in the test range off Naval Base Ventura County, Calif.

The target drone, which has no warhead, put what appears to be a 3-foot-wide hole in the cruiser’s port break, the throughway between the fo’c’sle and midships that is well above the waterline.

The sailors who suffered burns were treated aboard the ship.

The investigations. The Navy has launched two investigations to assess why the drone struck the ship. A safety investigation will be led by Naval Air Systems Command to determine what happened so that it can be prevented in the future. A command investigation, led by Capt. Rich Haidvogel, an official with Strike Force Training Pacific, is also underway to assess the mishap and recommend whether any participants should be reprimanded.

Officials have not disclosed any likely reasons why the Chukar III struck the cruiser.

‘Telemetry birds.’ Targeting drones like the Firebee are a routine part of combat systems testing. Known as “telemetry birds,” these remote-controlled aircraft fly trajectories that simulate enemy fighters or incoming missiles to test ships’ radar and weapon systems.

The Chukar III is a 13-foot-long drone that looks like a mini-Tomahawk and can be controlled by an operator remotely or can fly a preplanned route in “hands off” mode.

Rare mishap. For being involved in so many exercises, target drones have a low accident rate. But these exercises are dangerous, often with the ship firing its Close-in Weapons System, and ship crews take precautions, like staying clear of the weather decks.

It is believed to be the most serious mishap of a target drone striking a ship in three decades, since the Feb. 10, 1983, incident when splinters from an incoming drone struck the frigate Antrim, setting off a fire that killed a civilian professor onboard.